The Mouse-colored Tapaculo is usually considered to be endemic to the coastal mountains of southeast Brazil, where it inhabits humid montane forest below 2500 m. The species is generally fairly common, but is far more often heard than seen. Its plumage is unique among southeast Brazilian Scytalopus, with the exception of the exclusively wetland-inhabiting Marsh Tapaculo (Scytalopus iraiensis), in being basically all dark gray. Recent years have witnessed considerable upheaval in our knowledge of Brazilian tapaculos, especially in respect of this species. Firstly, those birds in the far south of the Mouse-colored Tapaculo’s range, namely in northeast Argentina and southernmost Brazil, were reassigned to a new species, Planalto Tapaculo (Scytalopus pachecoi). This was followed by considerable discussion concerning the correct application of the name Scytalopus speluncae, and the true identity of its holotype.